This invention relates to the purification and recovery of L-phenylalanine (hereinafter "phenylalanine") from an aqueous solution, typically from a microbial fermentation broth. By the method disclosed herein, substantially pure phenylalanine may be selectively recovered from the solution in a single crystallization step, notwithstanding the presence of other amino acids, color bodies, glucose, inorganic salts, extracellular proteins, organic acids, etc., in the original solution.
Phenylalanine traditionally has been difficult to purify from fermentation broths. The presence of inorganic salts, particularly those characteristic of precursor-based broths, renders separation by ion exchange inefficient. Alkali salts typically will be present which cannot be removed by conventional ion exchange methods without incurring a 20 to 30% phenylalanine loss unless multistep fractional crystallization or inefficient elution displacement techniques are used.
Under certain conditions, activated charcoal has been used to adsorb phenylalanine or a substituted phenylalanine from a culture broth. Examples of these uses are found in U.S. Pat. No. 3,759,790 and U.S. Pat. No. 3,917,511 (Nakayama et al.), which disclose mixture with active carbon and elution, followed by passage through a column of strongly acidic cation exchange resin. U.S. Pat. No. 3,767,528 (Nagasaki et al.) discloses adsorption of 3,4-dimethoxyphenyl-L-alanine on active charcoal and eluting with water as the first step of a four-cystallization recovery. Greenstein et al., "Chromatography", Chemistry of Amino Acids, p. 1459 (1961), describes a sequence of events employed in the separation of amino acids from a protein hydrolysate, in which aromatic amino acids were adsorbed on charcoal and the resulting effluent was passed through a series of ion exhanges to yield individual amino acids.